A low cost, light density cryogenic insulation capable of resisting high temperature is needed to insulate an expendable cryogenic fuel tank having outer space applications. It must be an efficient thermal insulator to minimize liquid hydrogen boil-off, and have good ablation properties to protect the tank structure from the high temperature encountered during ascent. Ablation tests and thermal conductivity tests performed on polyurethane ablative foams reveal them to be low density efficient ablators and have low thermal conductivity. The fibers added to the foams provide high shear strength to resist thermal contraction loads and a strong base to bond the insulation to the tank structure.
Polyurethane foam eliminates the need of a two-component system, one to satisfy the cryogenic insulation requirements and the other to serve as an ablator to provide high temperature protection. This reduces material and manufacturing costs, and weight, and increases reliability of the material.